North and South Korean border guards traded fire Tuesday across the heavily armed demilitarized zone between their nations. There are no reports of injuries.

A South Korean military official says the shooting took place 40 kilometers northeast of Seoul around 11 am local time.

Army Major Yoon Won-shik says two or three shots were fired from a North Korean guard post, breaking a window at the South Korean guard post but causing no injuries.

In response, South Korean guards broadcast warning messages and fired about 15 rounds. Tuesday's incident took place within the four kilometer-wide Demilitarized Zone, which divides the Korean peninsula.

South Korea says a team of United Nations officials will visit the site to determine the nature of the North Korean shots.

The two countries share the world's most heavily fortified border, with nearly two-million troops deployed on both sides. There have been previous shooting incidents since 1953, the year the Korean War ended without a peace treaty.

Inter-Korean reconciliation efforts, which flowered last year following an historic summit, have recently stalled. The latest round of bilateral talks broke down earlier this month and plans for a fourth reunion of divided families were put on hold.

The main obstacle appears to be the state of military alert in Seoul, which began after the September 11th terrorist attacks in the United States. Seoul says it is unrelated to North Korea, but Pyongyang accuses Seoul of lying.

In addition, political analysts say, a year of tensions between Washington and Pyongyang have led to fewer constructive exchanges between North and South Korea.